It is going to have to go back to Canon for that, it sounds like a failure in the display system. If it doesn't show up on captured images, then at least the image sensor wasn't damaged.
Mirrorless cameras are like video cameras where the sensor is constantly exposed to light unlike a DSLR so they can be inadvertently damaged by exposure to intense light such as lasers used for light shows or letting it accidentally point at the sun for an extended period while not being used.
Early failure of electronics components is unfortunately less rare than it should be. My experience with Canon service has always been very good so reach out to them to set up a warranty repair.